Low cost disposable needleless injector system for variable and fixed dose applications

ABSTRACT

A disposable needleless injection device includes an integral unit that is dimensioned and arranged to be grasped in the hand of a user. The system is spring-loaded and is manufactured and shipped with the spring in a pre-cocked condition. An integral ampule is fillable by manipulation of a thrust rod/shaft which extends longitudinally through the device and is able to be grasped by a user. Once the unit is filled with a selected medication, it is held proximate the skin in order to inject the selected dosage. The unit is constructed from a maximum of eight component parts and is assembled in a matter of moments by unskilled personnel.

PRIORITY CLAIM

This patent application claims the benefit of the filing date of U.S.provisional patent Application No. 60/195,389, filed on Apr. 7, 2000,entitled LOW COST DISPOSABLE NEEDLELESS INJECTOR SYSTEM FOR VARIABLE ANDFIXED DOSE APPLICATIONS, the entire contents of which is herebyexpressly incorporated by reference.

FIELD OF THE INVENTION

The present invention relates generally to needleless hypodermic drugdelivery devices and methods. The present invention relates moreparticularly to a low cost, disposable, spring actuated needlelessinjection device which utilizes a high pressure liquid stream to injecta medicament or other liquid through the skin and also relates moreparticularly to a method for using and manufacturing the same.

BACKGROUND OF THE INVENTION

Needleless injection devices which administer intramuscular and/orsubcutaneous medications without the use of a needle are well known.Among the many advantages of such needleless injection devices are thereduction of pain and apprehension commonly associated with hypodermicneedles, the elimination of needle stick injuries, and the reduction ofenvironmental pollution associated with contaminated needle disposal.Moreover, needleless injection devices are useful in a wide range ofdrug therapies, including the administration of vaccines, hormonetherapies and local anesthetics. Further, it is well known that suchneedleless injection devices are useful in the administration of insulinto the diabetic population, where individuals frequently require anumber of daily injections.

Injectable medications fall into two different general categories,namely: unit dose drugs such as vaccines and analgesics; and variabledose drugs such as insulin, where the dose size must be adjustedspecifically so as to meet the immediate needs of the individual at thetime of administration. When a variable dose is required, as in the caseof the administration of insulin, a very accurate amount of medicationmust be transferred to a variable dose ampule of the needlelessinjector. Insulin doses are typically marketed in 3 ml and 5 ml syringecartridges, as well as being provided in bulk in a standard 10 mlmedication vial.

The use of needleless injection devices has recently become of greatinterest, particularly by people of limited physical abilities such asthe elderly, the very young and the infirm. Such persons with limitedphysical abilities may find the use of conventional needle syringeseither difficult or impossible. Therefore, the simplified injectionprocess associated with needleless injectors makes their use verydesirable among such people.

The principles of needleless injection and the advantages of suchneedleless drug delivery systems over conventional hypodermic needleinjection systems have long been known. However, very few needlelessinjection devices have achieved commercial success in the marketplace.This lack of acceptance by the user community can be attributed, atleast in part, to a number of factors, chief among which are: mechanicaldesigns which have the potential to inflict serious injury if aninjector device is inadvertently fired without a medicament container orampule in place, undesirably complex filling techniques, and the highcost of such contemporary injection devices. This cost disadvantage isparticularly troublesome for those individuals who must self-administera large number of daily injections, such as diabetics.

One existing needleless injection device is described in U.S. Pat. No.4,874,367 to Edwards. It employs a sealed ampule that is prefilled witha selected amount of medication. The prefilled ampule is attached to aseparate spring-loaded firing mechanism which, when triggered, propels aramrod from the front of the mechanism and against a plunger located inthe ampule. The ramrod drives the plunger against the medication,producing a high pressured jet for injection purposes. The plungerexpels the medication from a discharge orifice and into the patient'ssubcutaneous tissue.

Although effective in some respects, this contemporary needlelessinjection device is severely limited in practical applications. In orderto cock the firing mechanism, the user is required to force the ramrodback into the firing mechanism by pushing the device against a solidsurface, such as a table top, until the ramrod latches behind a triggermechanism. Thus, the strength of an individual user imposes a strictlimit upon the spring force that can be utilized in the device. Manyelderly, very young or infirm people simply do not have the physicalstrength required to cock the firing mechanism of such a contemporaryneedleless injection device.

Moreover, employing a spring force which is low enough to be practicalfor the elderly, the very young and the infirm to cock the deviceresults in the spring force being inadequate to produce effective andreliable injection pressures for most adults. That is, such a devicewould generally lack the ability to penetrate the skin and subcutaneoustissue sufficiently to insure proper, reliable, operation thereof.

In addition, the firing mechanism, having a spring actuated ramrod whichextends outside of the device body, has the potential to inflict seriousinjury if inadvertently fired without the ampule in place. For example,firing such a device without having the ampule attached thereto mayresult in harm to a person who is inadvertently struck with the rapidlymoving ramrod.

Moreover, the fixed dose ampule of contemporary needleless injectiondevices such as those of the '367 patent must be prefilled at thefactory and then attached to the injector when required for usage. Inactual practice, however, this procedure is not practical for the simplereason that drug products cannot generally be stored in plasticcontainers for the extended periods of time which are typicallyexperienced by such factory prefilled ampules. The only approvedmaterial for long term liquid medication storage is type-1 glass, whichis used for virtually all drug products. However, due to the dynamics ofneedleless injection, in which the ampule is subjected to very highpressures during the ejection process, glass is not a suitable materialfor the ampule because it is too easily shattered. Consequently, it isdesirable to have an ampule which may be coupled to a conventional drugvial or other medication container at the time of use, and then befilled therefrom with an accurate dose of medication. The ampule shouldbe made of a high strength plastic material.

Indeed, the needleless injection device of U.S. Pat. No. 4,874,367 isformed of durable materials and utilizes comparatively expensivemanufacturing techniques, so as to assure long time reliable usethereof. As such, this device is comparatively expensive to manufacture.The expense associated with the manufacture of this device precludes thesale and use of this device as a single use, disposable needlelessinjector.

U.S. Pat. No. 4,913,699 to Parsons overcomes some of the aforementioneddeficiencies associated with contemporary needleless injectors. Thispatent describes a disposable needleless injection device having afiring mechanism that operates to release compressed gas from a storagecompartment. The compressed gas acts upon a piston which drives aplunger that ejects a selected dosage of medication through an aperturein the discharge end of the device. However, the medication to beadministered must first be drawn into a chamber provided in the interiorof the injector before being dispensed. Thus, although being pre-cocked,and loadable (with medicine), the device is rather complicated to use.In addition, no provision is made for filling the medication chamberdirectly from standard medication containers. In order to fill themedication chamber, a complex liquid transfer system is required.

The device disclosed in the '699 patent is relatively complex. It ismanufactured from materials able to withstand the pressures associatedwith a compressed gas activation system. Indeed, this needlelessinjection device is formed of comparatively durable materials andutilizes comparatively expensive manufacturing techniques, so as toassure long term reliable operation thereof in light of theaforementioned pressures. As such, this device is comparativelyexpensive to manufacture. The expense associated with the manufacture ofthis device precludes its sale and use as a single use, disposable item.

Thus, although the aforementioned contemporary needleless injectionsystems are compact and reliable, they are too complex and expensive tomanufacture in order to be considered disposable.

In view of the foregoing, it is clear that there is a need in the artfor a needleless hypodermic injection device which has an enhancedsimplicity of design and which can be manufactured from a small numberof low cost components in order to be implemented as a truly disposablesystem. Furthermore, there is a need for a needleless hypodermicinjection system which includes a medication ampule which is capable ofbeing filled with an accurate dose of medication and which does notimpose a risk of injury due to needle use and which does not contributeto the contamination hazards attendant with needle disposal.

In this regard, it is desirable to provide a convenient, low cost anddisposable needleless injector device that is configured to beconveniently and comfortably grasped in one hand of a user in a mannerwhich facilitates self-administration of a desired medication. Thesystem should comprise a firing mechanism and an ampule cooperating in anovel design having simplicity in both structure and function. Theampule should be such that the user may fill it with a selected dosageconveniently and accurately from existing medication vials, so as tofacilitate both variable and fixed dose applications. The injectorfiring mechanism should be conveniently and safely operated without theneed for a user to force the apparatus against a piece of furniture orthe like in order to cock a spring. There should be no substantialdanger associated with firing the device without an ampule in place.

SUMMARY OF THE INVENTION

The present invention specifically addresses and alleviates theabove-mentioned deficiencies associated with the prior art. Moreparticularly, the present invention comprises a housing and a springinjector mechanism disposed at least partially within the housing.Preferably, the spring injector mechanism and/or the housing areconfigured to be used only one time.

Preferably, the needleless injector of the present invention is providedwith a spring injector mechanism which is already compressed or cockedwhen purchased, such that the user does not have to cock the device.Thus, the needleless injector of the present invention is particularlysuitable for the elderly, the very young and the infirm.

Further, the needleless injector of the present invention is preferablyconfigured such that it is generally suitable for only a single use.

Thus, according to the present invention, a low cost, disposableneedleless injector is provided, so as to facilitate the administrationof injections such as vaccines, hormones, local anesthetics and insulin.

It is understood that changes in the specific structure shown anddescribed may be made within the scope of the claims without departingfrom the spirit of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects and advantages of the presentinvention will be more fully understood when considered with respect tothe following detailed description, appended claims and accompanyingdrawings, wherein:

FIG. 1 is a semi-schematic side view of the low cost, disposableneedleless injector of the present invention, as it is provided by asupplier, i.e., cocked and having an empty ampule;

FIG. 2 is a semi-schematic top view of the needleless injector of FIG.1;

FIG. 3 is a semi-schematic cross-sectional end view of the needlelessinjector taken along line 3 of FIG. 2;

FIG. 4 is a semi-schematic cross-sectional end view of the needlelessinjector taken along line 4 of FIG. 2;

FIG. 5 is a semi-schematic cross-sectional side view of the needlelessinjector of FIG. 1;

FIG. 6 is a semi-schematic side view of one housing section; i.e., thehousing section opposite that which is shown in FIG. 1;

FIG. 7 is a semi-schematic side view of the shaft of FIG. 1;

FIG. 8 is a semi-schematic side view of the plunger of FIG. 1;

FIG. 9 is a semi-schematic side view of the piston of FIG. 5;

FIG. 10 is a semi-schematic perspective view of the safety slide of FIG.1;

FIG. 11 is a semi-schematic perspective view of the trigger of FIG. 1;

FIG. 12 is a semi-schematic perspective view of an exemplary one of thetwo elastomeric washers or cushions of FIG. 5;

FIG. 13 is a semi-schematic side view of the ampule of FIG. 1;

FIG. 14 is a semi-schematic cross-sectional side view of the needlelessinjector of FIG. 1, wherein the shaft is positioned within the ampule ata location corresponding to approximately 0.05 ml of medication beingpresent in the ampule;

FIG. 15 is a semi-schematic cross-sectional side view of the needlelessinjector of FIG. 1, wherein the shaft is positioned within the ampule ata location corresponding to approximately 0.30 ml of medication beingpresent in the ampule;

FIG. 16 is a semi-schematic cross-sectional side view of the needlelessinjector of FIG. 1, showing the configuration of the trigger, spring,piston, and shaft after the trigger has been depressed so as to actuatethe spring injector mechanism;

FIG. 17 is a semi-schematic cross-sectional view showing the shoulder 29and the cushions, 31 and 32;

FIG. 18 is a semi-schematic perspective view of a package for a singleneedleless injector according to the present invention;

FIG. 19 is a semi-schematic perspective view of a volume efficientcluster of packages for containing a plurality of the needlelessinjectors of the present invention, wherein a plurality of singleneedleless injector packages have been formed to one another;

FIG. 20 is a semi-schematic perspective view of the cluster of packagesof FIG. 19, which has been rotated 180° about the longitudinal axisthereof;

FIG. 21 is a semi-schematic end view of the cluster of packages of FIGS.19 and 20, showing the distal end thereof; and

FIG. 22 is a semi-schematic end view of the cluster of packages of FIGS.19 and 20, showing the proximal end thereof.

DETAILED DESCRIPTION OF THE INVENTION

The detailed description set forth below in connection with the appendeddrawings is intended as a description of the presently preferredembodiment of the invention, and is not intended to represent the onlyform in which the present invention may be constructed or utilized. Thedescription sets forth the construction and functions of the invention,as well as the sequence of steps for operating the invention inconnection with the illustrated embodiment. It is to be understood,however, that the same or equivalent functions may be accomplished bydifferent embodiments that are also intended to be encompassed withinthe spirit and scope of the invention.

According to the present invention, a low cost, disposable needlelessinjector is provided so as to facilitate the administration of drugtherapies such as vaccines, hormones, local anesthetics and insulin. Thedisposable needleless injector of the present invention is pre-cocked atthe factory, so as to eliminate any need for a user to cock theneedleless injector. Thus, the disposable needleless injector of thepresent invention is well suited for use by the elderly, the very youngand the infirm, as well as any other persons who may find cocking ofsuch devices difficult and/or unsafe. This device is also very easy forhealthcare workers and the like to use on a patient. Thus, the presentinvention is well suited for both the self-administration of medicationand for the injection of others, such as by healthcare workers.

The needleless injector of the present invention is specificallyconfigured so as to be suitable for only a single use. Suchconfiguration of the present invention is accomplished, at least inpart, via the selection of particular materials which provide safe andreliable operation for a single use, but which are not suitable forindefinitely repeated use thereof. Single use of the needleless injectorof the present invention is further facilitated by the mechanical designthereof, which readily facilitates cocking of the device at the factory,but which substantially inhibits cocking by a user. Indeed, cocking ofthe present invention by a user is virtually impossible.

Further, the needleless injector of the present invention preferably hasan ampule permanently attached thereto, such that repeated use isinhibited and such that any hazard associated with firing of the devicewith an ampule not attached thereto is substantially mitigated.

More particularly, the low cost, disposable needleless injector of thepresent invention comprises a housing and a spring injector mechanismdisposed at least partially within the housing. The spring injectormechanism and/or the housing are configured specifically so as to beused only a single time. For example, the spring injector mechanism isconfigured so as to inhibit cocking thereof by a user, such as byproviding a shaft which cannot easily be grasped and pulled in a mannerwhich is necessary to effect cocking of the needleless injector. Thus,the spring injector mechanism is configured so as to require a speciallydesigned machine tool to facilitate cocking thereof. Of course, thismachine tool is not available to the general public.

Those skilled in the art will appreciate that various locks, catches,latches, detents and the like may be utilized to prevent re-cocking ofthe spring injector mechanism. For example, actuation of the springinjector mechanism may trip a latch which prevents further movement,i.e., re-cocking, of a shaft of the spring injector mechanism. Such alatch would be disposed within the housing, and thus not be easilydisengaged by a user. In this manner, a user is substantially inhibitedfrom re-cocking the spring injector mechanism, so as to facilitate reusethereof. Those skilled in the art will appreciate that various other,different methods for mechanically locking at least a portion of thespring injector mechanism in the fired position, after a single usethereof, are likewise suitable for inhibiting re-use of the presentinvention.

As stated above, the housing and/or the spring injector mechanism areconfigured so as to be unsuitable for indefinitely repeated use of thepresent invention. This may alternatively be accomplished, for example,by utilizing materials which inhibit repeated use thereof. Thus, theneedleless injector of the present invention is preferably formed ofmaterials which are insufficiently durable so as to facilitate repeateduse thereof. That is, the low cost disposable needleless injector of thepresent invention is formed of materials which are sufficiently durableas to safely and reliably facilitate a single use thereof, but whichwill not withstand the forces and pressures associated with repeated usethereof.

For example, the housing is preferably formed of an inexpensive andsufficiently durable (for a single use) polymer material, such as glassloaded acrylonitrile-butadiene-styrene (ABS) or such as polycarbonate.If the housing is formed of glass loaded acrylonitrile-butadiene-styrene(ABS), the acrylonitrile-butadiene-styrene (ABS) preferably comprisesapproximately 15% to approximately 20% glass. This particularformulation of acrylonitrile-butadiene-styrene (ABS) has been found tobe sufficiently durable to reliably and safely facilitate a single useof the present invention, while being insufficiently durable as tofacilitate indefinitely repeated use thereof. Further, bothacrylonitrile-butadiene-styrene (ABS) and polycarbonate are sufficientlyinexpensive as to facilitate the provision of a truly disposable device.The housing is preferably formed of two separate housing sections whichare substantially mirror images of one another, so as to furthermitigate cost. Preferably, multiple cavity injection molds are used toform the housing.

As discussed in detail below, the plunger and the two resilientcushions, all of which are preferably simultaneously co-molded to theshaft, are all formed of Santoprene. While Santoprene is sufficientlydurable for a single use of the present invention, Santoprene is notsufficiently durable for indefinitely repeated use thereof. Repeated useof the present invention will result in degradation of the Santoprenecomponents thereof and thus render the present invention unsuitable forfurther use. In particular, the cushions will tend to deformsubstantially with each use, such that they rapidly loose their abilityto function as shock absorbers.

A trigger for the needleless injector of the present invention ispreferably formed of stamped stainless steel sheet. Such a stampedstainless steel trigger is sufficiently durable as to facilitate singleuse thereof. The stamped stainless steel trigger is also sufficientlyinexpensive as to facilitate the construction of a truly disposabledevice. The trigger may be polished, if desired, so as to enhance theappearance thereof, since the cost associated with such polishing isnegligible.

The trigger is preferably formed in a stair-stepped configuration, so asto eliminate the need for a pivot pin therefor and thus further reducecosts, as discussed in detail below.

The spring injector mechanism preferably comprises a spring disposedwithin the housing, a piston configured to be moved by the spring and ashaft configured to be moved by the piston. The spring preferablycomprises a closed, but not ground, music wire helical spring.Eliminating grinding of the spring further reduces cost withoutimpairing the reliability or safety of the present invention.

The piston preferably comprises a die cast zinc, copper and aluminumalloy. The proportions of zinc, copper and aluminum are selected toprovide the mass necessary to eject fluid from an ampule with thenecessary force as to effect a subcutaneous injection. The use of suchan alloy provides the necessary mass to drive the shaft in a manner thatassures proper operation of the present invention, e.g., the developmentof pressure within the ampule of approximately 3,000-3,500 psi. The useof this alloy also reduces costs sufficiently to facilitate theconstruction of a disposable device.

The shaft preferably comprises polycarbonate having approximately 15%glass or a glass loaded polymer of equivalent performance such as Amodel(a federally registered trademark of Amoco Oil Company of Chicago,Ill.). The use of such a polycarbonate shaft provides sufficientdurability to facilitate a single use of the present invention, whileinhibiting indefinitely repeated use thereof. Further, thispolycarbonate shaft reduces the cost of the needleless injector, so asto facilitate the construction of a truly disposable device.

According to the present invention, the shaft is a single piece orunitary construction member and extends completely through the housingand into the ampule. The shaft extends from the proximal end of thehousing such that the spring injector mechanism may be cocked by pullingthe shaft proximally. As mentioned above, the shaft is preferablyconfigured so as to inhibit grasping thereof, in order to similarlyinhibit cocking of the spring injector mechanism by a user. Rather, thespring injector mechanism is cocked at the factory by a machine which isspecifically configured to grasp the proximal end of the shaft and pullthe proximal end of the shaft proximally with respect to the housing.

Such single piece or integral construction of the shaft has a furtheradvantage, in that it readily facilitates filling of the ampule with adesired quantity of medication in a simple and accurate manner. Theampule may be filled by manipulating the proximal end of the shaft.Manipulating the proximal end of the shaft similarly manipulates thedistal end thereof, so as to draw fluid into the ampule or expel fluidfrom the ampule in a very precise manner.

The ampule is permanently attached to the housing, such that access tothe distal end of the shaft is inhibited, thereby preventing the springinjector mechanism from being cocked by pushing the distal end of theshaft against a surface (as is done according to some contemporaryneedleless injectors) Permanently attaching the ampule to the housingfurther mitigates a danger associated with dry firing or actuating theneedleless injector without medicine in the ampule. Although the shaftis driven forcible in the distal direction when the needleless injectoris dry fired, the permanently attached ampule prevents the moving shaftfrom striking anything other than the ampule itself.

The ampule is preferably threadedly attached to the housing, and theneither adhesively bonded or sonically welded thereto. Permanentattachment of the ampule to the housing not only enhances safety bymitigating the ability to fire the needleless injector with the ampuleremoved and facilitates single use of the needleless injector byinhibiting refilling of the ampule due to sterility concerns, but alsoreduces the cost of the present invention. The cost of the presentinvention is reduced by eliminating the need to form threads within thehousing which are suitable for repeated attachment and removal of theampule. That is, according to the present invention, the threads maymerely be injected molded as a part of the two housing sections and neednot be formed or touched up via machining or the use of a tap. Rather,the threads which are integrally injected molded with the two housingsections are sufficient for a single use of the present invention,particularly when the ampule is further attached to the housing viaadhesive bonding and/or sonic welding. Indeed, the housing need notcomprise any threads for attaching the ampule thereto, but rather mayalternatively utilize any desired injection moldable structure for thispurpose. For example, threads may be eliminated from both the housingand the ampule and the ampule may merely be inserted into the housingand permanently bonded thereto.

The needleless injector of the present invention is more particularlydescribed below with reference to FIGS. 1-16 of the drawings, whichdepict a presently preferred embodiment thereof. FIGS. 17-21 depict avolume efficient package for the needleless injector of the presentinvention, so as to substantially reduce the transportation and storagecost associated therewith, and thereby further facilitate the provisionof a truly disposable device. As shown in FIG. 1, the needlelessinjector of the present invention is provided to a user in asubstantially ready-to-use condition, requiring only that the ampule befilled with a particular medicament prior to injection.

Referring now to FIGS. 1-13, the low cost disposable needleless injector10 of the present invention generally comprises a housing 8 and a springinjector mechanism 9 disposed partially within the housing. The housing8 is generally cylindrical, approximately four inches in lengthexcluding the ampule, and approximately one-half inch in diameter. Theampule is approximately one and five-eighths inch in length andapproximately three-eighths inch in diameter.

The housing 8 is shaped such that it is easily grasped in the hand of auser, and when appropriately oriented, presents a depressable triggermechanism in the vicinity of the user's thumb or finger. Indeed, thehousing and trigger are configured such that when the housing is graspedwithin a user's hand, the trigger may be depressed either by the thumb,a finger or by merely squeezing the device in the user's hand or fist.The trigger has sufficient surface area and leverage to make the presentinvention easily actuatable by the elderly, the very young and theinfirm. Moreover, the configuration and positioning of the triggerreadily facilitates actuation by persons in a debilitated or weakenedstate and is even suitable for use in emergencies since a user does nothave to take time to carefully hold and/or position the device in aparticular manner. The device may be held in any manner which isconvenient for the person administering the injection. It is merelynecessary that the device be held in close contact to the skin,preferably generally perpendicularly thereto, and that the trigger thenbe depressed. The trigger is positioned to facilitate use of the presentinvention for the self-administration of medicine, as well as tofacilitate the administration of medicine to patients by healthcareworkers in any desired manner, e.g., with a thumb, finger, or bysqueezing the entire device in a person's hand or fist.

The housing 8 preferably comprises first and second housing sectionswhich are preferably injection molded either fromacrylonitrile-butadiene-styrene (ABS) loaded with approximately 15% toapproximately 20% glass or is alternatively injection molded frompolycarbonate. The housing 8 has a proximal end and a distal end aslabeled in FIG. 1. All references to proximal and distal herein usethese terms as defined in FIG. 1. It is the distal end of the device(more particularly, the distal end of the ampule 50) which is pressedagainst the skin of a person who is to receive an injection.

Forming the housing 8 as two separate housing sections reduces thecomplexity and cost associated with the molding process, since anunthreading mold would be required if a unitary construction housingwere to be provided with female threads in order to receive the ampule.As those skilled in the art will appreciate, such unthreading molds areconsiderably more expensive than simple release molds, and would thusundesirably increase the cost of the needleless injector of the presentinvention.

An additional advantageous feature afforded by forming the housing astwo separate housing sections is appreciated during the assemblyprocess, wherein the device may be assembled by simply placing thecomponents into one of the two housing sections and then positioning theother housing section thereover. The two housing sections are bonded toone another using adhesive, sonic welding, or any other desired method.

More particularly, the assembly process comprises inserting a shaft 25through the piston 15. The resilient washers 31 and 32 and the plunger26 have previously been co-molded or over-molded to the shaft of theshaft 25. The spring 13 is then slid over the sleeve 17 of the piston 15so as to define the spring injector mechanism 9. The spring injectormechanism 9 is then placed into one of the two housing sections. Thesafety slide 42 and the trigger 40 are similarly placed in the samehousing section. The other housing section is then mated thereto andbonding is effected. The ampule may then be screwed into the housing andbonded thereto. Alternatively, both the ampule and the housing may lackthreads, such that the ampule may simply be slid into the housing andbonded thereto. Those skilled in the art will appreciate that variousdifferent mechanical locking means for permanently attaching the ampuleto the housing are likewise suitable. Thus, the ampule may bemechanically locked to the housing and/or bonded thereto. Then theneedleless injector of the present invention may be cocked utilizing amachine which holds the housing in place, while pulling the shaft 25proximally, by grasping the ball 27 thereof. With the shaft 25 held inthe cocked position, the trigger 40 is moved to a position wherein thesear 37 thereof inhibits distal movement of the piston 15 and the safetyslide 42 is moved distally, so as to prevent undesirable movement of thetrigger 40.

The spring is preferably a closed, but not ground, music wire helicalspring 13 (best shown in FIGS. 5 and 14-16) which is disposed within thehousing such that the spring 13 has a cocked or compressedconfiguration, as shown in FIGS. 5, 14 and 15 and also has a fired oruncompressed configuration as shown in FIG. 16. The spring 13 preferablyhas a spring constant of approximately 24 lbs./in. The spring ispreferably approximately 3 inches long and develops approximately 28lbs. of force when compressed so as to cock the spring injectionmechanism. The spring 13 is sized to slide freely within a bore 22 ofthe housing. The proximal end of the spring 13 bears upon shoulder 14formed within the housing and the distal end of the spring 13 bears upona piston 15 (best shown in FIG. 9).

The piston 15 comprises a sleeve 17 which is sized to be received withinthe spring 13. The sleeve 17 preferably has an outside diameter which issubstantially less than the inside diameter of the coil formed by thespring 13, such that the sleeve 17 moves freely along the inside of thespring without substantially frictionally engaging the spring 13.

The piston further comprises a head 19 which defines a shoulder 20against which the distal end of the spring 13 abuts. The head 19 of thepiston 15 is sized to slide freely within the bore 22. The pistonoptionally further comprises a conically tapered portion 21 of the head19. However, those skilled in the art will appreciate that the exactconfiguration, size and dimensions of the piston 15 will be determined,as least in part, by the mass thereof which is required to eject fluidfrom an ampule 50 with the necessary force to reliably perform aninjection. Thus, the mass of the piston 15 is determined by both itsdimensions and the materials from which it is formed, as discussedabove.

The ampule 50 is preferably substantially transparent, so as tofacilitate viewing of the quantity of liquid contained therein. A scaleis typically provided upon the ampule so as to provide a numericalindication of the quantity (typically in milliliters) of fluid containedtherein.

The spring injector mechanism 9 further comprises an elongated shaft 25(best shown in FIG. 7) having a plunger 26 (best shown in FIG. 8) formedupon the distal end thereof and having a cocking knob 27 formed upon theproximal end thereof. The plunger 26 is preferably formed of anelastomer or thermosetting rubber such as Santoprene manufactured bySonoco or the equivalent.

The plunger 26 is secured firmly to the shaft 25 via a shaft retainingheads 90 a and 90 b formed at the distal end of a portion 91 of theshaft 25 having a reduced diameter, as discussed in detail below.

The gripping ball 27 is preferably formed upon the proximal end of theshaft 25 by forming a reduced diameter neck 28 formed in the shaft 25near the proximal end thereof. The shaft 25 further comprises a portionof increased diameter or shoulder 29 formed thereon and disposed withinthe housing. The shoulder 29 is preferably formed integrally with theshaft 25. Alternatively, the shoulder 29 may be formed separately fromthe shaft 25 and be attached thereto. Resilient cushions 31 and 32 arepreferably disposed upon either side of the shoulder 29. Resilientcushion 31 cushions the impact of the piston 15 when the piston movesforward and strikes the shoulder 29 of the shaft 25 so as to cause theshaft 25 to eject fluid, as described in detail below. Similarly,resilient cushion 32 cushions the impact of the shoulder 29 of the shaft25, when the shoulder 29 strikes a proximal portion of the ampule 50during the fluid injection process, as also discussed in detail below.Both resilient cushions, 31 and 32, thus cooperate to mitigate noise andrecoil when the device is operated. The mitigation of noise and recoilis important, so that the device is perceived as user friendly. Thoseskilled in the art will appreciate that excessive noise and recoil maybe associated with pain or discomfort, and are thus undesirable.

As shown in FIG. 1, the needleless injector 10 of the present inventionis configured as it is typically packaged and received by a user. Theampule 50 is empty, i.e., contains no medication when configured forvariable dose applications, and the shaft 25 is disposed partiallywithin the ampule 50 so as to reduce the overall length of the device tofacilitate volume efficient packaging thereof.

The first and second resilient cushions, 31 and 32, as well as theplunger 26, are all preferably injection molded to the shaft 25 during asingle injection co-molding process, and thus all preferably comprisethe same resilient thermosetting rubber material, e.g., Santoprene (afederally registered trademark of Monsanto Company of St. Louis, Mo.).The plunger 26 and the first and second cushions, 31 and 32, mayalternatively be formed of polyvinyl chloride (PVC) or silicone. Withparticular reference to FIG. 8, the plunger 26 preferably comprises acentral bore 24 ending in distally located hemispherical chambers 34 aand 34 b. The bore 24 is configured to receive the reduced diameterportion 91 of the shaft 25 and the chambers 34 a and 34 b are configuredto receive the heads 90 a and 90 b of the shaft 25, in a manner whichfacilitates secure attachment of the plunger 26 to the shaft of theshaft 25. The heads 90 a and 90 b of the plunger 25 preferably define aChristmas tree or conically barbed protrusion, such as those commonlyused to facilitate the attachment of an elastomeric component to a morerigid member.

The piston 15 is held in the cocked position thereof, against the forceof spring 13 by the trigger 40, which is preferably formed of stampedstainless steel. Preferably a rib 36 is formed longitudinally along asubstantial portion of the length of the trigger 40, so as to enhancethe structural strength thereof. As those skilled in the art willappreciate, the use of such a rib 36 allows the trigger 40 to be formedof substantially thinner sheet stainless steel, thereby further reducingthe cost thereof.

As best shown in FIG. 11, the trigger is formed in a stair-step likefashion, so as to define a sear 37, a lower portion 38, a middle portion39 and an upper portion 40. This stair-step configuration of the trigger35 facilitates reliable use thereof without the need for a pivot pin, soas to further mitigate costs.

Safety slide 42 (best shown in FIG. 10) is slideably attached to thehousing such that the safety slide has a distal position whereinmovement of the trigger 40 is inhibited so as to likewise inhibitactuation of the spring injection mechanism, and also has a proximalposition, wherein the trigger is free to move, as discussed in detailbelow. The distal position at the safety slide 42 thus mitigates thelikelihood of inadvertent actuation of the spring injector mechanism.The safety slide 42 preferably has ridges 43 formed thereon, so as tofacilitate easy operation thereof.

A flange 48 extends distally from the safety slide 42. When the safetyslide 42 is in its safe or distalmost position, the flange 48 covers aportion of the trigger 40, so as to inhibit actuation of the injectorspring mechanism, as discussed in detail below.

Female detents 47 (there is preferably one female detent on each side ofthe safety slide, cooperate with corresponding male detents formed uponthe first and second housing sections to releasably lock the safetyslide in the safe position (the distal most position) thereof, so as toinhibit inadvertent movement of the safety slide away from the safeposition thereof.

The ampule 50 (best shown in FIGS. 13 and 14-16) has a chamber 51 formedlongitudinally therein for containing medication. The ampule 50 ispreferably permanently attached to the housing via threads 53 formedupon the proximal end thereof and complementary threads 54 (best shownin FIG. 6) formed at the distal end of the housing. In addition tothreadedly attaching the ampule 50 to the housing, the ampule ispreferably adhesively bonded and/or sonically welded to the housing, soas to assure permanent attachment thereof.

As used herein, permanent attachment of the ampule to the housing isdefined as attachment of the ampule to the housing via bonding, such asadhesive bonding or sonic welding, and/or via mechanical fastening, in amanner which substantially inhibits removal of the ampule from thehousing by a user.

Indeed, according to the present invention the ampule is preferablyattached to the housing in such a manner that the ampule is not likelyto be removed from the housing by a user without damaging the device andrendering it unuseable.

The ampule 50 further comprises a tip 60 formed at the distal most endthereof. The tip 60 has a bore formed therein so as to facilitate fluidcommunication of the medicine from the chamber 51 and therethroughduring the injection process.

A Luer like threaded fitting or lug 62 is preferably formed proximatethe distal end of the ampule, so as to facilitate filling thereof. Theampule is preferably formed of polycarbonate and optionally comprises acontemporary ampule such as those commonly used in needleless injectiondevices.

Generally, the ampule is filled by affixing a transfer coupler to thefront end of the ampule and using the transfer coupler to access thecontents of either a standard drug vial, standard syringe cartridge, orthe like. Once the contents of the medication container are accessed,the injection device is filled by manipulating the shaft 25. The shaft25 is withdrawn or moved proximally so as to create a suction in thechamber 51 of the ampule 50, so as to effect extraction of medicationfrom the medication container.

For example, a user may move the shaft 25 to its distal most position,thereby forcing substantially all of the air from the ampule. The usermay then move the shaft 25 proximally, so as to produce suction withinthe chamber 51 of the ampule 50 and thus effect withdrawal of medicationfrom a vial into the chamber 51. Typically, the ampule will be filledwithin slightly more medication then is necessary for the desiredinjection, so that any air in the ampule can be ejected by simplyholding the needleless injector vertical, with the ampule uppermost, andthen pushing the shaft back into the ampule chamber slightly, so as toeffect ejection of any air within the ampule, as well as a smallquantity of medicine, as those skilled in the art will appreciate. Theuser may then verify that the correct dosage has been withdrawn into theampule by viewing the position of the plunger 26 within the ampule,relative to the graduations that are preferably provided upon thetransparent ampule. Since the ampule is generally overfilled slightly,the user may reduce the quantity of medicine contained within the ampuleby simply pushing the shaft 25 distally.

With particular reference to FIG. 6, the housing preferably comprises asecond housing section 12, which is substantially a mirror image of thefirst housing section 11. One distinction between the first and second,11 and 12, housing sections is that one of the two housing sections hasfirst, second, third and fourth guide pins, 71, 72, 73 and 74, as wellas guide slat 75 formed thereon. These guide members comprise male guidemembers, while on the other one the two housing sections, 12 and 11,complimentary female guide members are formed. The male and female guidemembers engage one another, so as to facilitate proper alignment of thetwo housing sections and so as to maintain the two housing sections insuch proper alignment during sonic welding of the first and second, 11and 12, housing sections to one another.

Each housing section, 11 and 12, comprises a groove 77 within which thesafety slide 42 is slideably disposed. A male detent 82 is preferablyformed within the groove 77 of each housing section so as to engage acorresponding female detent 47 of the safety slide 42 in a manner whichreleasably locks the safety slide 42 in the safe position, as discussedabove. Safety slide 42 comprises first 78 and second 79 flanges whichare received within the slots 77 of the first and second housingsections to facilitate slidable movement of the safety slide 42.

Both the first and second housing sections further comprise a taperedslot 80 within which the trigger 35 is pivotally disposed, as shown inFIGS. 5 and 14-16. The tapered slot 80 facilitates pivoting of thetrigger 35, in a see-saw like fashion, about angled edge 81 (FIG. 11) ofthe trigger such that when the distal end of the trigger 35 is depressedor pushed toward the housing, then the proximal end of the trigger 35,including the sear 37 thereof, moves upwardly, so as to effectdisengagement of the sear 37 from the piston and thereby actuate or firethe spring injection mechanism to effect an injection.

The needleless injector cannot easily be used more than one time due tothe difficulty associated with re-cocking thereof and/or due to theunsuitability of the materials and/or design for repeated reuse.

The needleless injector of the present invention is formed utilizing aminimum number of components, such that it may be manufactured in asimple fashion by unskilled workers.

Having described the structure of the low cost, disposable needlelessinjector in detail above, it may be beneficial to likewise describe theoperation thereof. Operation of the needleless injector is describedbelow with reference to FIGS. 14-16.

With particular reference to FIG. 14, the needleless injector 10 isshown with the shaft 25 positioned within the ampule 50 in a mannerwhich facilitates the injection of a comparatively small amount, e.g.,0.05 ml, of medicine. Similarly, FIG. 15 shows the shaft 25 positionedwithin the ampule 50 in a manner which facilitates the injection of acomparatively larger amount of medicine, e.g., approximately 0.30 ml.Thus, the shaft 25 can be moved to various positions within the ampule50, so as to facilitate the injection of various different quantities ofmedication, as is necessary for variable dose usage.

In both FIGS. 14 and 15, the spring 13 is compressed intermediate theshoulder 14 of the housing and the shoulder 20 of the piston 15. Thepiston 15 is maintained in this cocked position by the sear 37 of thetrigger 40. The safety slide 42 prevents actuation of the springinjector mechanism by preventing the trigger 40 from being depressedtoward the housing and thereby preventing the sear 37 from disengagingthe piston 15. Thus, the safety slide 42 tends to prevent accidentalactuation of the spring injector mechanism, which might result inaccidental injection of the medicine. In any event, accidental actuationof the spring injector mechanism of the present invention will renderthe device unusable, since the low cost disposable needleless injectorof the present invention is specifically configured for only a singleuse thereof.

The ampule 50 of the needleless injector of the present invention isloaded with medicine by attaching a vial or the like to the distal endof the ampule 50 and moving the shaft 25 proximally, so as to drawmedicine from the vial into the ampule 50, according to well knownprinciples.

Since the ampule is permanently affixed to the needleless injector ofthe present invention, there is no need for a user to have to insert,attach, or otherwise adapt the ampule to an injector, in order toperform an injection.

Preferably, the shaft 25 is placed in its distal most position prior toattaching the ampule 50 to the vial, such that there is very little orno air within the chamber 51 of the ampule 50. The quantity of medicinewith which the ampule 50 is filled can be read accurately from a scale(FIG. 13) formed upon the ampule 50. The ampule 50 may be slightly overfilled, if desired.

After filling the ampule, the injection site upon the person receivingthe injection and/or the distal end of the ampule 50 are sterilized,such as with alcohol, and the injection is then administered.

The injection is administered by holding the needleless injector 10generally perpendicular to the skin at the injection site and thendepressing the trigger 40, such as with the thumb of the hand holdingthe device. Prior to depressing the trigger, the safety slide 42 must bemoved proximally, so as to allow the sear 37 to disengage the piston 15.

After the trigger 40 has been depressed, and the sear 37 disengages thepiston 15, the spring 13 moves from its compressed position (as shown inFIGS. 14 and 15) to its uncompressed or extended position as shown inFIG. 16. As the spring 13 moves toward its uncompressed position, thespring 13 urges the piston 15 distally. As the piston 15 moves distally,the piston 15 strikes the first resilient washer 31 and causes the shaft25 to move distally along with the piston 15. The first resilient washer31 cushions the impact of the piston 19 with respect to the shoulder 29of the shaft 25.

It will be noted that there is a gap between the piston 15 and theshoulder 29, as shown in both FIGS. 14 and 15. This gap is the distancethat the piston 15 must travel before it strikes the cushion 31, whichis located just proximal of the shoulder 29. The length of the gap iswithin a range of gap lengths which are defined by the position of theplunger 26 within the ampule, as determined by the quantity ofmedication to be injected. Each gap length within this range of gaplengths is suitable for allowing the piston 15 to acceleratesufficiently before striking the cushion 31, so as to generate thedesired pressure (typically approximately 3,000 psi-5,000 psi) withinthe chamber 51 of the ampule 50.

As the spring 13 continues to move toward its extended position, theplunger 26 expels the medicine from the chamber 51 of the ampule 50,thereby effecting the injection. According to the preferred embodimentof the present invention, the spring 13 remains partially compressed inits fully extended position (as shown in FIG. 16) and therefore has apreload.

It is important to appreciate that after the injection has beeneffected, it would be extremely difficult for a user to re-cock thespring injector mechanism so as to effect the performance of anotherinjection with the needleless injector of the present invention. Theproximal end of the shaft 25 is specifically configured to inhibitgrasping thereof, as is necessary to effect re-cocking of the device.

Further, permanent attachment of the ampule 50 to the housing preventsthe attachment of a new, sterile ampule to the housing, as would bedesirable in the performance of another injection.

Referring now to FIG. 17, the shoulder 29 is shown to be integrallyformed with the shaft 25. Those skilled in the art will appreciate thatvarious other means of forming such a shoulder upon a shaft are likewisesuitable. For example, the should may alternatively be formed by addinga separately formed structural member to the shaft 25. The cushions 31and 32 are molded directly to the shaft 25 and the shoulder 29, asdiscussed in detail above.

Referring now to FIGS. 18-22, volume efficient packaging for theneedleless injector of the present invention is shown. As those skilledin the art will appreciate, it is important to reduce the various costsassociated with use of the needleless injector of the present invention,so as to make disposability thereof economically feasible. One importantaspect of such cost reduction involves the use of volume efficientpackaging, so as to mitigate transportation and storage costs associatedwith the present invention.

The packaging system of the present invention has been specificallydesigned so as to minimize the cost and the volume associated with thepackaging. Thus, according to the present invention, each package, asshown in FIG. 18 requires only slightly more volume than the needlelessinjector itself. Further, a cluster of packages as shown in FIGS. 19 and22 comprises interleaved individual packages which further minimizewasted space.

Wasted space is minimized in the cluster of packages by inserting orinterleaving one row of packages along with another row thereof. Thus,space between adjacent packages within a row, which is normally wasted,is efficiently utilized according to the present invention. That is, aneedleless injector in one row of packaging according to the presentinvention is disposed efficiently intermediate two adjacent needlelessinjectors of the other row thereof.

With particular reference to FIG. 18, each individual package 100 for aneedleless injector 10 according to the present invention, comprises acradle 101 and a cover 102. The cover 102 is preferably bonded, such asvia adhesive bonding to a planar surface 104 of the cradle 101. Thecradle 101 defines a cavity 103. The cover 102 completely covers andhermetically seals the cavity 103, so as to facilitate the provision ofa sterile environment for the needleless injector contained therein.Both the cradle 101 and the cover 102 are preferably transparent, sothat the presence of a needleless injector within the package 100 iseasily detected.

Each cradle 101 is preferably formed by vacuum forming sheet polymermaterial. Each cover 102 is preferably formed by cutting, die stampingor otherwise forming individual covers from roll or sheet polymer.

According to the preferred embodiment of the present invention, eachcorner of the cradle 101 comprises a bevel 105 which exposes acorresponding corner 107 of the cover 102, so that the cover 102 may beeasily grasped and peeled away from the cradle 101, as shown in FIG. 18.

The cradle preferably further comprises a plurality of ribs 109, whichenhance the structural strength thereof, and thus facilitate the use ofthinner material in the construction of the cradle, so as to furtherreduce the cost thereof.

The cavity 103 of the cradle 101 generally conforms in shape to theshape of the needleless injector, so as to minimize the cost of thepackaging, as well as the volume thereof.

When a plurality of such packages are placed in a row, i.e., side byside, then a gap is formed between adjacent packages. As discussedbelow, the present invention takes advantage of this gap betweenadjacent packages so as to further enhance the volumetric efficiencyassociated with the packaging of a plurality of needleless injectors.

With particular reference to FIGS. 19-22, a plurality of packages, suchas those of FIG. 18, are formed together in a cluster 110. The clustermay comprise either a plurality of individual packages, which have beenattached to one another, or may alternatively comprise one or morepluralities of individual packages which are formed together, integrallywith one another. For example, the cluster 110 may comprise twopluralities of packages or rows, 113 and 114, wherein each row, 113 and114, is formed integrally and separately from each other row, 114 and113, and then the two rows are attached to one another or interleaved.Thus, each row, 113 and 114, of the cluster 110, may be formedseparately by vacuum forming or the like, and then the rows may beinterleaved. This interleaving of the two rows enhances the volumeefficiency of the completed multiple needleless injector package is thusmore volume efficient and less costly.

The covers for each cradle in a row are either separately formed or areformed of one piece of material which is perforated or scored, such thatthe individual cover associated with a particular needleless injectormay be peeled away from the cradle so as to facilitate the removal of adesired particular needleless injector. The use of such separate coversfor each needleless injector facilitates the storage of the remainingneedleless injectors in a sterile environment after one or more of theneedleless injectors has been removed from such a cluster package.

The clusters may be formed such that they are easily broken apart, so asto form individual packages or so as to form smaller clusters. Scores orperforations may be utilized so as to facilitate such breaking apart ofa cluster. A cluster so scored or perforated may be formed so as tobreak apart into smaller clusters having any desired number ofindividual packages.

The cradles are preferably formed from a transparent polymer materialsuch as polyethylene terephalate glycol (PETG). The covers arepreferably comprised of a material such as Tyvek (a federally registeredtrademark of Dupont de Nemurs and Company of Wilmington, Del.).

According to the present invention, all of the components of the presentinvention, including the components of the packaging, are suitable forgamma sterilization. The needleless injector of the present invention ispackaged, either automatically or manually, by placing one needlelessinjector in the cavity of each cradle and then sealing the cover to theupper flat surface 104 of each cradle, so as to provide a hermetic seal.After hermetically sealing a needleless injector in each package of acluster (or in a non-cluster, single product package), then theneedleless injector(s) and associated package(s) are gamma sterilized.Gamma sterilization is performed after sealing of the needlelessinjectors within their packages so as to assure maintenance of propersterilization thereof, until the packages are opened by the user.

According to an alternative configuration of the present invention, theneedleless injector may be provided to the user with the ampuleanesceptically filled with a desired medicament. When the needlelessinjector is provided with the ampule prefilled, then the proximal mostportion of the shaft 25 is preferably cut off or otherwise removed, soas to inhibit movement thereof, which might tend to undesirably forcefluid from the ampule. That is, that portion of the shaft 25 which wouldotherwise extend from the proximal end of the housing is removed, so asto prevent the shaft 25 from being undesirably manipulated duringhandling. In this manner, fixed dose applications of the presentinvention are facilitated.

It is understood that the exemplary low cost, disposable needlelessinjector described herein and shown in the drawings represents only apresently preferred embodiment of the invention. Indeed, variousmodifications and additions may be made to such embodiment withoutdeparting from the spirit and scope of the invention. For example,various different configurations of the spring, piston and shaft arecontemplated. For example, those skilled in the art will appreciate thatthe piston may have various different configurations, shapes and/ordimensions which facilitate compression of the spring, locking of thespring in the compressed configuration thereof by the trigger, and whichhave the necessary mass so as to assure proper ejection of a fluid fromthe ampule when the shaft is struck thereby.

Thus, these and other modifications and additions may be obvious tothose skilled in the art and may be implemented to adapt the presentinvention for use in a variety of different applications.

What is claimed:
 1. A needleless injector comprising: a housing; aspring injector mechanism including a shaft disposed at least partiallywithin the housing and at least partially externally of the housing, thespring injector mechanism being configured to be used only one time; andwherein said shaft is configured to move in any axial direction evenwhen said spring injector mechanism is in a cocked position by graspingand moving the partially externally portion of the shaft.
 2. Theneedleless injector as recited in claim 1, wherein the spring injectormechanism is configured to inhibit cocking by a user.
 3. The needlelessinjector as recited in claim 1, wherein the spring injector mechanism isconfigured to require a tool to facilitate cocking thereof.
 4. Theneedleless injector as recited in claim 1, wherein at least one of thehousing and the spring injector mechanism is configured to be unsuitablefor repeated use thereof.
 5. The needleless injector as recited in claim1, wherein at least one of the housing and the spring injector mechanismis configured to be unsuitable for indefinitely repeated use thereof. 6.The needleless injector as recited in claim 1, wherein at least one ofthe housing and the spring injector mechanism is formed of materialwhich inhibits repeated use thereof.
 7. The needleless injector asrecited in claim 1, wherein at least one of the housing and the springinjector mechanism is formed so as to be insufficiently durable as tofacilitate repeated use thereof.
 8. The needleless injector as recitedin claim 1, wherein the housing is formed of a polymer material.
 9. Theneedleless injector as recited in claim 1, wherein the housing comprisestwo injection molded polymer housing sections which are sonically weldedto one another.
 10. The needleless injector as recited in claim 1,wherein the housing is formed of glass loadedacrylonitrile-butadiene-styrene (ABS).
 11. The needleless injector asrecited in claim 1, wherein a trigger is formed of stamped sheet metal.12. The needleless injector as recited in claim 1, wherein a trigger isformed of stamped sheet stainless steel.
 13. The needleless injector asrecited in claim 1, wherein a trigger is formed in a stair-steppedconfiguration to eliminate a need for a pivot pin therefor.
 14. Theneedleless injector as recited in claim 1, wherein the spring injectormechanism comprises: a spring disposed within the housing; a pistonconfigured to be moved by the spring; and a shaft configured to be movedby the piston.
 15. The needleless injector as recited in claim 1,wherein the spring injector mechanism comprises: a spring disposedwithin the housing; a piston configured to be moved by the spring; and aglass reinforced polymer shaft configured to be moved by the piston. 16.The needleless injector as recited in claim 1, wherein the springinjector mechanism comprises: a spring disposed within the housing; apiston configured to be moved by the spring; and a shaft configured tobe moved by the piston; wherein the shaft is configured to inhibitgrasping thereof so as to inhibit cocking of the spring injectormechanism.
 17. The needleless injector as recited in claim 1, furthercomprising an ampule from which the shaft forces fluid when the shaft ismoved.
 18. The needleless injector as recited in claim 1, furthercomprising an ampule permanently attached to the housing.
 19. Theneedleless injector as recited in claim 1, further comprising an ampulethreadedly attached and adhesively bonded to the housing.
 20. Theneedleless injector as recited in claim 1, further comprising an ampulethreadedly attached and sonically welded to the housing.
 21. Theneedleless injector as recited in claim 1, wherein the spring injectormechanism comprises a closed, but not ground, music wire helical spring.22. The needleless injector as recited in claim 1, wherein: the housingcomprises: two housing sections formed of injection molded plastic andconfigured to be substantially mirror images of one another; the springinjector mechanism comprises: a spring disposed within the housing; apiston configured to be moved by the spring; and a shaft configured tobe moved by the piston.
 23. A needleless injector comprising: a housing;a spring injector mechanism comprising a shaft, a piston, and a springdisposed at least partially within the housing and at least partiallyoutside of the housing, the spring injector mechanism being configuredto cause fluid to be injected; and wherein the spring injector mechanismis cocked by grasping at least a portion of the shaft that is outside ofthe housing, and the shaft, subsequent to the cocking, remains moveablerelative to the piston.
 24. A needleless injector comprising: a polymerhousing having proximal and distal ends; an aluminum piston slidablydisposed within the housing; a music wire helical spring disposed withinthe housing and configured to urge the piston toward the distal end ofthe housing when the spring is released; a glass reinforced polymershaft disposed at least partially within the housing and partiallyoutside of the housing and configured to be moved distally by thepiston; a stamped sheet steel trigger attached to the housing andconfigured to release the spring; and wherein the injector is cocked bypulling on the shaft section that is partially outside of the housingwhich pulls the piston until the piston is engaged by the trigger; andwherein the shaft remains movable in any axial direction even after theinjector is cocked.
 25. A low cost, disposable needleless injectorsystem comprising: a needleless spring injector mechanism; an ampulepermanently attached to the needleless spring injector mechanism fromwhich fluid is forced by the needleless spring injector mechanism, andwherein said spring injector mechanism includes a shaft and wherein saidshaft is configured to be pulled to cock the spring injector mechanismand wherein the shaft remains moveable subsequent to the cocking of thespring injector mechanism.
 26. The low cost, disposable needlelessinjector system as recited in claim 25, wherein the ampule is adhesivelybonded to the needleless spring injector.
 27. The low cost, disposableneedleless injector system as recited in claim 25, wherein the ampule issonically welded to the needleless spring injector.
 28. The low cost,disposable needleless injector system as recited in claim 25, whereinthe ampule is integrally formed with respect to the needleless springinjector.
 29. A needleless injector system comprising: a housing havingproximal and distal ends; a piston slidably disposed within the housing;a spring disposed within the housing and configured to urge the pistontoward the distal end of the housing when the spring is released; ashaft configured to cock the needleless injector system disposed atleast partially within the housing and partially outside of the housingand configured to be moved distally by the piston; a trigger attached tothe housing and configured to release the spring; an ampule disposedproximate the distal end of the housing and configured to receive atleast a portion of the shaft; wherein when the shaft moves toward anaperture of the ampule, fluid disposed within the ampule is forcedtherefrom through the aperture; and wherein the housing, piston, spring,shaft and trigger are configured to generally provide only one injectionby configuring a proximal end of the shaft with a surface that issufficiently small to limit a user's ability to generate sufficientcocking force with the user's bare hand.
 30. A method for performing aninjection, the method comprising: releasing a spring force to therebymove a shaft that is partially coaxially disposed within a piston andadapted to move relative to the piston; injecting fluid with aneedleless spring injector; and disposing of essentially all of theneedleless injector after injecting the fluid only one time.
 31. Themethod as recited in claim 30, wherein the needleless spring injector isconfigured to be disposable.
 32. The method as recited in claim 30,wherein the step of injecting fluid with a needleless spring injectorcomprises moving a trigger so as to release a compressed spring, thespring moving a piston toward a distal end of the needleless springinjector, the piston moving a shaft to toward the distal end of theneedleless spring injector and the shaft forcing fluid from an ampule.33. The method as recited in claim 30, wherein the needleless springinjector comprises: a housing; and a spring injector mechanism disposedat least partially within the housing, the spring injector mechanismbeing configured to be used only one time.
 34. The method as recited inclaim 33, wherein the spring injector mechanism is configured to inhibitcocking by a user.
 35. The method as recited in claim 33, wherein thespring injector mechanism is configured to require a tool to facilitatecocking thereof.
 36. The method as recited in claim 33, wherein at leastone of the housing and the spring injector mechanism is configured to beunsuitable for repeated use thereof.
 37. The method as recited in claim33, wherein at least one of the housing and the spring injectormechanism is configured to be unsuitable for indefinitely repeated usethereof.
 38. The method as recited in claim 33, wherein at least one ofthe housing and the spring injector mechanism is formed of materialwhich inhibits repeated use thereof.
 39. The method as recited in claim33, wherein at least one of the housing and the spring injectormechanism is formed so as to be insufficiently durable as to facilitaterepeated use thereof.
 40. The method as recited in claim 33, wherein thehousing is formed of a polymer material.
 41. The method as recited inclaim 33, wherein the housing comprises two injection molded polymerhousing sections which are sonically welded to one another.
 42. Themethod as recited in claim 33, wherein the housing is formed of glassloaded acrylonitrile-butadiene-styrene (ABS).
 43. The method as recitedin claim 33, further comprising a trigger for actuating the springinjector mechanism and wherein the trigger is formed of stamped sheetmetal.
 44. The method as recited in claim 33, further comprising atrigger for actuating the spring injector mechanism and wherein thetrigger is formed of stamped sheet steel.
 45. The method as recited inclaim 33, further comprising a trigger for actuating the spring injectormechanism and the trigger is formed in a stair-stepped configuration toeliminate a need for a pivot pin therefor.
 46. The method as recited inclaim 33, wherein the spring injector mechanism comprises: a springdisposed within the housing; a piston configured to be moved by thespring; and a shaft configured to be moved by the piston.
 47. The methodas recited in claim 33, wherein the spring injector mechanism comprises:a spring disposed within the housing; a piston configured to be moved bythe spring; and a glass reinforced polymer shaft configured to be movedby the piston.
 48. The method as recited in claim 33, wherein the springinjector mechanism comprises: a spring disposed within the housing; apiston configured to be moved by the spring; and a shaft configured tobe moved by the piston; wherein the shaft is configured to inhibitgrasping thereof so as to inhibit cocking of the spring injectormechanism.
 49. The method as recited in claim 48, further comprising anampule from which the shaft forces fluid when the shaft is moved. 50.The method as recited in claim 48, further comprising an ampulepermanently attached to the housing.
 51. The method as recited in claim48, further comprising an ampule threadedly attached and adhesivelybonded to the housing.
 52. The method as recited in claim 48, furthercomprising an ampule threadedly attached and sonically welded to thehousing.
 53. The method as recited in claim 33, wherein the springinjector mechanism comprises a closed, but not ground, music wirehelical spring.
 54. The method as recited in claim 33, wherein thehousing and the spring injection mechanism are configured to bedisposable.
 55. A needleless injector made according to the methodcomprising: forming a housing from a non-metallic material; placing aspring injector assembly at least partially within the housing; andwherein the step of placing the spring injector assembly at leastpartially within the housing comprises: placing a generally annularpiston slidably upon a shaft, the shaft being slidable relative to thepiston; placing a helical compression spring slidable upon the piston;and placing the piston, shaft and the spring into the housing such thata portion of the shaft extends out of the housing for grasping by auser.
 56. A needleless injector comprising: spring means for forcingfluid from an ampule to perform an injection, the spring meanscomprising a shaft partially coaxially disposed within a piston; housingmeans for containing the spring injector means; and wherein both thespring means and the housing means are useable only one time by makingthe spring means substantially incapable of resetting with a user's barehand.
 57. A method for performing an injection, the method comprisingthe steps of: performing an injection step for forcing fluid from anampule via a needleless spring injector, the needleless spring injectorcomprising a shaft partially coaxially disposed within a piston; andperforming a disposal step for disposing essentially the entireneedleless spring injector after only one use.
 58. A needleless injectorcomprising: a housing; a spring disposed within the housing; a pistonconfigured to be moved by the spring; and a shaft configured to be movedby the piston; wherein the shaft extends from a proximal end of thehousing and out of the housing to facilitate filling an ampule disposedat a distal end of the housing by grasping on the portion of the shaftthat extends out of the housing with a user's bare hand and moving theshaft relative to the piston.
 59. The needleless injector as recited inclaim 58, wherein the shaft extends from the distal end of the housingto facilitate ejection of fluid from an ampule.
 60. A needleless unitdose injector comprising: a housing; a spring disposed within thehousing; a piston configured to be moved by the spring; a shaftconfigured to be moved by the piston; and an ampule containingmedication; wherein a proximal portion of the shaft has been removedfrom a distal portion of the shaft after the proximal portion of theshaft has been used to cock the shaft to deter recocking.
 61. Aneedleless injector assembly comprising a housing having a distal end, aproximal end, and a longitudinal exterior surface; an ampule attached tothe distal end of the housing; a spring injector assembly disposed atleast partially within the housing, the spring injector assemblycomprising a shaft partially coaxially disposed within a piston and aspring coaxially disposed over at least a portion of the piston; a leverfor engaging the piston to keep the spring injector assembly in a cockedposition; a trigger having a squeezing surface positioned adjacent thelongitudinal exterior surface of the housing adapted to move the leverwhich then releases the piston; and wherein the shaft comprises aproximal end in fluid communication with the ampule and a distal endthat extends from the distal end of the housing.
 62. The needlelessinjector assembly of claim 61, wherein the spring injector assembly iscocked by pulling on the distal end of the shaft that extends from thedistal end of the housing so that the lever engages the piston.
 63. Aneedleless injector assembly comprising a housing having a distal endand a proximal end, an ampule for containing a fluid attached to thedistal end of the housing, a spring injector assembly comprising a shaftpartially coaxially disposed within a piston and the piston coaxiallydisposed with a spring, wherein the shaft comprises a proximal end thatextends from the proximal end of the housing, a distal end that isadapted to pass inside the ampule, and a shoulder disposed in betweenthe proximal end and the distal end of the shaft, and wherein the pistoncomprises a piston head for pushing the shoulder; a lever for contactingwith the piston head to maintain the spring injector assembly in acocked positioned; and a trigger for squeezing, which when squeezed isadapted to remove the contact between the lever and the piston head tothereby permit the piston to be propelled by the spring.
 64. Theneedleless injector assembly of claim 63, further comprising a safetymechanism for preventing the trigger from being squeezed when activated.65. A method for delivering medication contained inside an injectorassembly subcutaneously without a needle comprising the steps: cocking aspring injector assembly disposed at least partially within a housing;the spring injector assembly comprising a piston comprising a pistonhead, a shaft coaxially disposed with the piston and having a proximalend, a distal end, and a shoulder disposed in between the proximal endand the distal end, and a spring coaxially disposed with the piston;filling the injector assembly with medication by filling an ampuleattached to a distal end of the housing with medication; and firing thespring injector assembly by placing the ampule next to a surface of abody and pulling on a trigger disposed on a side of the housing; whereinthe step of cocking the spring injector assembly comprises the step ofpulling on the proximal end of the shaft to cause the shoulder to pushagainst the piston head until a lever engages the piston head tomaintain the spring injector assembly in the cocked position; andwherein the step of filling the injector assembly comprises the step ofgrasping on the proximal end of the shaft and moving the proximal end ofthe shaft from a first position to a second position after the pistonhas been cocked.
 66. The method of claim 65, further comprising the stepof disposing substantially all of the injector assembly after the firingstep.